Research on nutritional differences among different types of buds in Xanthoceras sorbifolium Bunge.

Xanthoceras sorbifolium Bunge is an important woody oil plant variety found in northern China. As a monoecious species, increasing the ratio of female-to-male flowers can effectively increase yield. X. sorbifolium has three bud types: female flower buds that preponderantly populate the upper section of the shoot, male flower buds chiefly concentrated in the middle segment of the shoot, and withered buds predominantly lodged in the lower portion of the shoots. This study aimed to identify the effects of nutrition on bud formation. Leaves, shoots, and buds were divided into upper, middle, and lower types based on their morphological location. The nitrogen (N), phosphorus (P), potassium (K), soluble sugar, and starch contents of the samples were measured during bud differentiation. Different concentrations of foliar N were applied before sexual differentiation to verify whether N significantly affected female flower formation. The results showed that N and P significantly affected female flower formation, whereas K contributed to male flower generation. Female flower development may require more soluble sugars, whereas male flower development may require more starch. Mixed bud differentiation required more N and P than did leaf-bud differentiation. High N concentrations (0.5 and 0.8%) increased the number of female flowers on lateral inflorescences and improved the female-to-male flower ratio. N treatment advanced flowering time, and the 0.5% treatment showed the most apparent effect (4 days earlier). These results contribute to a better understanding of the effects of nutrition and establish a solid foundation for modulating the female-to-male ratio from a nutritional perspective in X. sorbifolium.